DESCRIPTION: This proposal is aimed at characterizing the pathway for -1-In the first aim, recordings will be used to characterize response patterns in the auditory pathway. In the second aim chronic recordings will be used to track changes in response patterns from the beginnings of song development in the young to song crystallization in the adult. In adult birds, auditory feedback is inhibited in the nucleus HVc. This proposal will test the hypothesis that little or no inhibition will be found in the HVc in young birds prior to song crystallization. During the critical periods of template matching and song development, it is proposed that such inhibition would interfere with the necessary flow of feedback through the HVc to the anterior forebrain loop. Adult levels of inhibition in the HVc are expected only after songs have crystallized into adult patterns. Preliminary records from chronic implants in free-flying adults have been made in Field L, the source of auditory input to the HVc.